U.S. Severe Weather Forecast (Coup d'œil sur la convection)

Day Three

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Storm Prediction Center ac 201618 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1118 am CDT Monday Oct 20 2014 

Valid 201630z - 211200z 

..no severe thunderstorm areas forecast... 

isolated to widely scattered thunderstorms are probable today across 
parts of the Ohio Valley...South Florida...and from south Texas into 
the southern rockies. Isolated storms are also possible today along 
the Pacific coast from Washington to northern California...and into 
the northern Great Basin by tonight. 

A pronounced midlevel trough near Chicago will progress eastward over the 
Ohio Valley by this afternoon...and reach the middle Atlantic coast early 
Tuesday morning. Weak buoyancy accompanying the band of ascent 
immediately in advance of the trough will support a continued risk 
for isolated thunderstorms into this evening from NE Indiana across 
Ohio. Rapid air mass modification will occur through tonight as the 
wave approaches the Atlantic coast...though thunderstorm development 
should occur just offshore. 

Another northern stream trough will move inland over the Pacific today and 
the northern Great Basin by the end of the period. Isolated lightning 
strikes will be possible with low-topped convection along the 
baroclinic zone and in the onshore flow/Post-frontal regime...and 
the thunderstorm risk will extend as far S as the Sacramento Valley 
of northern California. Isolated strikes may also occur farther inland tonight 
across the northern Great Basin...where ascent coincides with weak 
midlevel buoyancy. Elsewhere...widely-scattered thunderstorms are 
expected across the southern rockies in advance of a weak southern stream 
trough near the Arizona/nm/Mexico border region...and across S Texas/S Florida 
within the north/NE fringe of the moisture plume associated with the 
weak tropical low in the Bay of Campeche. 

.Thompson/Rogers.. 10/20/2014 

Mesoscale Discussion

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sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 151720 

Mesoscale discussion 1899 
National Weather Service Storm Prediction Center Norman OK 
1220 PM CDT Wednesday Oct 15 2014 

Areas affected...central Maryland into southeastern PA 

Concerning...severe potential...watch unlikely 

Valid 151720z - 151945z 

Probability of watch issuance...20 percent 

Summary...an isolated strong wind gust or brief/weak tornado cannot 
be ruled out with storms as they develop northward from Maryland into southeastern PA. 

Discussion...an isolated strong cell with substantial vertical 
development continues to propagate northward along a north-S oriented boundary 
which extends into PA and links with an existing front across eastern PA 
which currently separates the more moist/unstable air to the southeast. 

This particular storm has had a persistent and broad circulation 
with it...but nothing particularly strong or tight probably due to 
weak low-level buoyancy/acceleration. While deep-layer flow is 
strong above the ground...most of the shear is relegated to the 
near-surface layer and other cells away from the outflow boundary 
have shown little if any shear. Therefore...any wind/tornados threat is 
expected to be brief...short-lived and isolated...and a watch is not 

.Jewell/corfidi.. 10/15/2014 

..please see www.Spc.NOAA.Gov for graphic product... 


Latitude...Lon 39157664 39007677 38987688 39067699 39267696 39617690 
40007679 40347640 40457615 40407593 40137594 39617620